1. Field of the Invention
The present invention relates to a power supply circuit, and more particularly, to a power supply circuit capable of improving the power factors of a high input voltage.
2. Description of the Prior Art
Many industry standards are made for standardizing the power efficiency of electronic products in order to achieve the goal of saving energy. For example, some of the industry standards require the power factor of a power supply circuit to be 0.9 or above. Most of the electronic products comply with the input voltage of 100-240 volts (V), and when the input voltage is lower, the requirement of the high power factor can be fulfilled more easily. However, when the input voltage is higher, it is hard to fulfill the requirement of the high power factor. When an electronic product adopts a high input voltage, the input current thereof is relatively small in comparison with an input current under a low input voltage. Hence, the goal of correcting the power factor cannot be achieved effectively, making the power factor fail to meet the related requirements of energy saving. Therefore, there is a need for a novel method and associated architecture to improve the power factor under the high input voltage.